Process of purifying oil



. SePt' 1S, 1934. c. w. GARRISON 1,973,895

I PROCESS OF PURIFYING OIL Filed March 10, 1930 1N VEN TOR .v Obra/Ice dGar/vaan.

Patented Sept. 18, 1934 P Artur Clarence fW-.yGarrisonfFcrt Wayne,Ind.,.assign0r .to TheKoppers `Company of Delaware, a corporation of'Delaware Application March-10, 1930,`Seria'l No. 434,490

, liquid and is therefore uneconomical for the rear son that fresh:amounts of :sodium'hydroxide or 'its equivalent must be employed `foreachcorref spending unit o'i' impurity removed.

An object of my invention is the provision oi raprocess of and apparatusfor purifying oil in which 'the purifying 'liquid is substantiallycontinuously recirculated.through a cycle including a regenerationstage, so that it is used again and again.

A further object of my'invention is the provision of aprocess o'f and'apparatus for purifying oil in a continuous 'and cyclic 'manner Where-'by the optimum eiciency of absorption of `irnpurities may be realized.

My invention has for further objects such 'other operations, advantagesor .results as may hereinafter 'be foundto obtain.A l

My .invention contemplates the `substantially continuous washing of theoil to4 be puried with a regenerable purifying liquid,.that is, a

liquid capable of absorbing hydrogen sulphide or analogous impuritiesfrom the oil in amounts suiiicient to accomplish a worthwhilepurification `of the oil and .of then being rendered ca pable of furtheruse 'for the 'saine'fpurplose by treatment with air, heating, reactionwith a substance having a greaterjafiinityior hydrogen sulphide than'the liquid 'itself `or any other treatment which canbe carried outsubstantial# ly Without interrupting thecyclic recirculation of theVpurifying liquid. ,n

, -By ,regeneration .is meant merely `the` renewal .of lat-least asubstantial .portion'oi the original capacity of the'liquid for`absorption of .the im.- purity theremoval-of vwhich is desired, but notnecessarily a re-creationfnf .the compound Yo1 vcompounds originallypresent linthe vliquider a .return to Athe `full original .capacity ofsaid liquid forabsorbing said impurity.

I preferto employ as the purifying liquid a solution containing acompoundv oran alkali# forming Vmetal or radical such, for example, assodium, potassium, calcium, magnesium or ammonium and of these Iordinarily prefer a compound of sodium as being the most advantageous`with 'respect lto the ultimate'economy'of the system. l

' For example, I may `employ a solution 'of sodium carbonate. Aso'lution'of sodium hydroxide itself may be used inthe first instance,`a's fo'r example in starting upthe process,` but 'in this case it isnecessary in order to regenerate or kactify the solution 'in order ytointroduce carbon dioxide either as va gas or 'in solution, or "someother acidic substance of about the 'same strength.

When employing a simple solution of sodium carbonate, for example, offrom 1 to `6`% alkalinity, 'the ifegeneration 'or actication afterabsorption of impurity from the 'oil treated may be accomplished bysubjecting the solution to a current of ygas such as Jair or 'other gascontaining little 'or no hydrogen sulphide, or by heating the solution,or both, .the reaction involved being a simple reversal of the'absorption reaction brought about by the .reduction of the partialpressure of lfiydrogenr sulphide in th'e `atmosphere adjacent vto :thesolution. A

'if a solution of caustic soda is employed in the first instance, itvshould be, 'as above .set forth, regenerated at iirst inthe presence of'carbon dioxide `but upon subsequent conversion of the active sodiumVinto sodium `carbonate or ibicarb'onate, iu'rth'er regeneration may beeffected by means 'of a gas containing no "carbon dioxide.

Other solutions may also, be employed, for example, a solution preparedby dissolving soL dium carbonate and arsenous oxide in Water 'therebyforming, as is Well known, a regenerable arsenic compound, which `may'comprise a 'sodium thioarsenate 'after initial Contact with thesulphuijladen oil. When such solutions are ernployed, the regenerationo'r acftilcat'ion involves the liberation ofyeleniental sulphur aiid-adifferent type of vreaction than ris true whenv a simple sodium'carbonate solution Vused, and air or other 'gas 'containing free oxygenmust `then be' used in order to secure yp'ro'pel" a'ctifica'tiori andregeneration.

" Moreover, "in such'insftan'ces it is Ordinarily desirabletof providesuitable 'rn'eans for substantially continuously .removing the liberatedsulphur', and inview ofthe fact .that the'oxyge'n contained in theactifying lgas itself enters into the reaction, it is also desirable toprovide ap 'paratus vfherebythe 'efficiency ,of introduction or theactifying 'gas to the solutonfis promoted. For exampla'rneansfor."introducing the gas in yan-vided form te a' body ofthe liquid tobe` ac d may 'be employed, thereby .also 'facilie tating theremoval ofsulphur by flotation. j

In any event, in order to achieve a continuous process capable ofemployment over extended periods of time, the extent of the actinfilcation or regeneration must be such as to remove from the recirculatedpurifying liquid an amount of the impurity or impurities (either as suchor in some other form) absorbed from the oil at least equal to theamount continuously removed from the oil treated. This does not,however, preclude the building up in the initial stages of the processof a certain amount of dissolved hydrogen sulphide which thereafterremains in the purifying liquid throughout the entire cycle ofrecirculation.V

Among the advantages of the use of arsenical solutions of the characterindicated for oil purification are the facts that such solutions areeffective to remove certain organic sulphur impurities, such asmercaptans, from the oil, which is not generally true of simple sodiumcarbonate solutions or alkaline suspensions of iron or nickel compounds,and the absence of purifying compounds in suspension, which are subjectto loss through entrainment by the oil as well as by the liberatedsulphur.

Iny order that myv invention may be fully set forth and understood I nowdescribe, with reference to the accompanying drawing, a preferred formand a preferred manner in which my invention is embodied and practiced.In the drawing;

The single ligure is a more or less diagrammatic view, partly inelevation and partly in vertical section, of apparatus for effecting thesubstantially continuous and cyclic purication of an oil by means of aregenerable purifying liquid.

Referring to the drawing, an oil to be purified from hydrogen sulphideis supplied from a source 1. This oil is conveyed by a pump 2 or anyother suitable device through a conduit 3 terminating in an opening 4within an oil treating chamber or absorber 5.

In the present instance it is assumed that the oil to be treated has alower specific gravity than the purifying solution and for this reasonthe oil is introduced to the absorber in the lower portion thereof butpreferably still somewhat removed from the bottom of the absorber 5. Theoil introduced through the opening 4 passes upward through the tower 5in countercurrent to a flow of purifying liquid introduced above thepoint of introduction with the oil through an opening 6 ina conduit 7.The oil, by reason of its lower specinc ravity, ultimately reaches thetop of the absorber 5 and passes out through a conduit 8 having a vent9.

The solution introduced through the conduit 'I to the absorber 5 maycomprise a solution originally prepared by dissolving sodium carbonatein water and having a total alkalinity of from 1 to 6%. By reason ofitshigher specinc gravity it passes downward through theabsorber 5 incountercurrent to the rising ow of oil and during this intimatecountercurrent contact absorbsr hydrogen sulphide` from the oil, therebypurifying the latter. The thereby fouled solution reaching the bottom ofthe absorber 5 is withdrawn through a sealed conduit 11 having a vent 12and `one of a plurality of .oftakes 13 located at suitable levels withvrespect to the mixture of liquids withink the absorber 5. The solutionpasses through the appropriate offtake 13 and a conduit 14 into a fouledliquid tank 15 from which it is substantially continuously delivered bymeans of a pump 16 through a conduit 17 and sprays 18 to an actifier 20.

The actifier 20 is of any suitable design, for example, an upright towerpartially filled with wooden hurdles 21 or other suitable gas-andliquidcontact'media. It is provided at the bottom with a conduit 22 forintroducing the actifying gas and an outlet 23 for removing the sameafter contact with the fouled liquid. In the present instance air isemployed as the actifying gas, being drawn from the atmosphere asdesired by a fan 24 connected with the conduit 22.

The fouled solution passes downward through the actifler 20 and throughcontact with the rising current of air is deprived of hydrogen sulphide.The thereby actified solution collects in a reservoir 25, which isconveniently located at the bottom of the actifier 20, and is thenforced by a pump 26 through the conduit '7 into the `abscrber forfurther contact with oil.

The purifying liquid is thus substantially continuously recirculatedthrough a cycle comprising the absorber 5 and the actier 20 and there isaccomplished on the one hand a purification of the flowing oil and onthe other a regeneration or revivication of the purifying liquid.

During the continuance of the process, mechanical losses whichinevitably occur and certain side reactions ordinarily take place. Theseresult in the consumption of sodium or its equivalent for the formationof inert side products, such as sodium thiosulphate, and make itnecessary to supply the recirculating liquid from time to time withfurther amounts of sodium carbonate or its equivalent. Similarly,portions of the recirculating solution may be discarded from time totime in order to limit the building up of inert materials in therecirculating system.

The foul actier air leaving the actierr 20 may be'sirnply wasted intothe atmosphere, or it may be used for combustion purposes, or it may bepurified in any suitable manner when so desired.

As a typical example of my process, it may be desired to purify apetroleum oil containing 0.15% by weight of hydrogen sulphide perAgallon with a degree of puricaton of y90%. For this purpose, I mayemploy a solution containing sodium carbonate and sodium bicarbonate ofapproximately 2% total alkalinity. In the absorption stage 0.9 gallonsof this solution are introduced per gallon of oil introduced and in theactication stage from 0.5 to 2 cubic feet of air are passed through thesolution per grain of hydrogen sulphide removed from the oil. However,as will be appreciated by those skilled in the art, these figures willvary considerably according to the type of apparatus employed, thetemperature of the recirculating liquid and the like'y and such detailsof operation are ordinarily best determined by experiment. y l

My invention is not limited to the specific details or examples setforth hereinabove but may variously be employed and embodied within thescope of the claimuhereinafter made.

'I claim as my invention:

The process of purifying hydrocarbon oil from sulphur contained as animpurity in said oil, which comprises subjecting the oil to contact withan aqueous solution of sodium carbonate and arsenous oxide.

CLARENCE W. GARRISON.

